Consequences of problematic prescription opioid consumption (which includes heavy use and misuse) and overdose have reached epidemic proportions in the United States and are a major public health concern. A number of repercussions associated with problematic opioid consumption and overdose, including co-morbid health problems and deaths, add to the seriousness of this issue. Strategies, such as Prescription Drug Monitoring Programs, have had a limited impact on access to opioids and overdose. There is a growing need for approaches that addresses both physicians' prescribing as well as consumers' use of opioid medications. Preferred drug formularies and utilization management tools stand to be valuable strategies for payers to control prescribing, consumption, and subsequent overdose. Previous studies of formulary and preferred drug list implementation in commercial and public plans have demonstrated reductions in prescription filling among a number of medication classes. Furthermore, research has shown that shifting medications to prior authorization lists results in prescription decreases. However, little is know about how provider factors and formularies influence opioid consumption and overdose. This study will examine the effect of formulary management strategies on patterns of problematic prescription opioid consumption and overdose in the Pennsylvania Medicaid program. Medicaid is an important payer for prescription opioids and covers a vulnerable population at high risk of opioid misuse. Pennsylvania has the 4th largest Medicaid program in the country and has long-standing contracts with several managed care organizations, each of which develops its own formulary and approach to managing drug utilization. As such, we can take advantage of rich cross-sectional and longitudinal variation in formulary design in an insurance program covering more than 2 million people annually between 2007-2012. With these data, the study will: 1. identify patient- and provider-level risk factors associated with opioid overdose and trajectories of opioid consumption that precede overdose in Medicaid and 2. examine effects of formulary/utilization management tools on overdose and problematic use. This study will enrich our understanding of the effects of formularies on prescription opioid use among Medicaid enrollees. Results from this study will be directly disseminated to Pennsylvania Medicaid program administrators who can implement statewide policies to slow or reduce problematic prescription opioid consumption, overdoses, and death.